1. Field of the Invention
The present invention relates to a brushless DC motor and an image pickup apparatus.
2. Description of the Related Art
It is conventionally known to apply a brushless DC motor that uses a coil for a stator and a magnet for a rotor, to a driving apparatus of a camera lens. See Japanese Patent Publication No. 06-67259. The brushless DC motor detects a position of the rotor through a sensor, and advantageously prevents stepping out by maintaining synchronization between a command signal and the position of the rotor.
Characteristically, a speed of the brushless DC motor depends upon a load. For a lens driving apparatus, the load fluctuates depending upon a position and a moving direction of the driving apparatus due to an unsteadiness-removing biased spring and a change of an inclination of an angle-of-view controlling cam groove. Therefore, a driving apparatus that uses the brushless DC motor changes its speed in driving a lens, and causes a user to feel uncomfortable.